Nobody wants to admit it, but marriage can be terrifying. This is especially true of the early phases, when you’ve realized that you aren’t just you anymore: there’s always you and someone else from then on. It’s perhaps a mild identity crisis, but a notable one all the same. In Honeymoon, writer/director Leigh Janiak explores and literalizes this and other marital anxieties with a deceptively simple cabin-in-the-woods tale that’s less about flesh-ripping ghouls and more about mysterious forces slowly ripping a loved one from your grip.

Bea and Paul (Rosie Leslie and Harry Treadaway) are one of those irritatingly lovey-dovey couples. They have their own little in-jokes and phrases, a sappy engagement story, and they’ve even recorded video messages to themselves to watch after their wedding. But they’re mostly good kids and certainly don’t deserve the fate awaiting them on their honeymoon. Their retreat to Bea’s family cabin starts out idyllic enough with an abundance of sex, pancakes, and boating. Things take an odd turn, however, when Bea runs into a childhood friend (Ben Huber) and his wife (Hanna Brown) during a disturbing encounter that puts everyone on edge. When Bea sleepwalks into the woods later that night, Paul grows even more disturbed—especially when he’s not even sure he’s brought his wife back.

Sure, the woman who returns to the cabin looks like Bea, but something is decidedly off about her. Not only is she suddenly forgetful, but she’s also weirdly vacant. With the help of her two leads, Janiak turns the film on a dime: it’s like watching someone’s vacation footage segue right into their funeral. It’s truly minimalist filmmaking to boot, powered mostly by the mere suggestion that something is wrong. With the exception of some flashing lights outside of the couple’s window and some mysterious sores that develop on Bea’s legs, Janiak provides little in the way of explicit imagery.

Instead, Honeymoon is a remarkable slow burn driven by a couple of affecting performances couched in an eerie backwoods atmosphere. By placing the supernatural aspects on the backburner, Janiak foregrounds the heart-rending domestic drama that unfolds between Bea and Paul. Leslie is especially revelatory in a role that asks her to subtly play slightly different variations on the same theme. As Bea, she’s bubbly and sweet; as Bea’s “replacement,” she tries to replicate this behavior, but she’s just a shade off. Appropriately, she isn’t all there, and Treadaway’s increasingly desperate performance plays off of Leslie’s dissipating humanity to create tension from a relatable situation: what would you do if you suddenly didn’t recognize the person you loved?

Honeymoon preys on such fears in a big way, so much so that the mystery surrounding Bea’s transformation is less pertinent than the possibility that Paul can somehow recover his wife’s soul. The notion is truly horrifying, and Janiak pushes it to all of its logical—or perhaps illogical—extremes as “bad” escalates to “worse” and “worse” escalates to “oh, fuck!” Watching it is like witnessing the worst fears about your marriage coming true: first, your spouse’s identity slowly begins to creep away, then they become confused, angry, and hostile, making Honeymoon somewhat of an Alzheimer’s parable until it becomes even darker. From Paul’s perspective, the events especially test his masculine insecurities—if the presence of his wife’s old summer fling weren’t enough, then his inability to protect his wife from a more ominous force is truly beguiling.

Of course, it’s just as horrifying from Bea’s perspective, and it’s noteworthy that the first phases of her changed are marked by her struggles to complete domestic tasks, such as making French toast and brewing coffee. It feels like a specifically feminine anxiety, one that’s compounded with her growing need to satisfy Paul. Whatever has inhabited Bea’s body goes through the routine of being a dutiful wife: it leaps into freezing cold water because “it’s funny,” and she rehearses lines in a mirror to repeat for Paul later. When it fails, their relationship completely breaks down, and Bea’s existential crisis becomes plain when she begins scribbling down her own name and details about her life. Her marriage to the force taking control of her body has consumed her.

Honeymoon is so effective in its implications that it barely needs to dabble in its climactic body horror. Far be it from me to be too hard on a decision that involves weird goo and a horrifying sequence that taps into anxieties surrounding the birthing process. During the course of a couple of days, Bea and Paul run the gamut of a relationship, and it’s all worst-case-scenarios, from this impromptu stillbirth to a climax that tests the whole “till death do us part” vow. When their honeymoon phase is over, it’s really over. This should be required viewing for all newlyweds, as I’m sure it beats counseling. Sometimes, catharsis is the best therapy. Buy it!